The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Both active and passive electronically scanned antennas (ESAs), also commonly referred to as phased array antennas, typically comprise multiple antenna radiating elements, sometimes referred to as radiators, individual element control circuits, a signal distribution network, beam steering control circuitry, a power supply and a mechanical support structure. The total gain, effective isotropic radiated power (“EIRP”) (for a transmit antenna) and scanning and side lobe requirements of the antenna are directly related to the diameter of the antenna's aperture, the number of radiators in the antenna aperture, the individual radiator spacing and the performance of the radiators and element electronics. In many applications, thousands of independent radiators and related control circuits are required to achieve a desired antenna performance.
A phased array antenna typically implements independent electronic packages, also referred to as transmit and receive (T/R) modules, for each radiator that are interconnected to a signal distribution circuit board, e.g., a printed wiring board (PWB). To avoid grating lobes, typical ESAs require that antenna radiators with controllable phases be spaced approximately one-half wavelength apart. Additionally, as the antenna operating frequency (and/or beam scan angle) increases, the required spacing between the radiators decreases. Thus, as the antenna operating frequency increases, the spacing between T/R modules also decreases, which increases the number of T/R modules for a fixed aperture diameter.
As the spacing of the radiators and related T/R modules decreases, it becomes increasingly difficult to physically configure the control electronics, i.e., the T/R modules, relative to the tight element spacing. This can affect the performance of the antenna and/or increase its cost, size and complexity. Consequently, the performance of a phased array antenna becomes limited by the need to tightly package and interconnect the antenna radiators and T/R modules associated therewith. For easing the mechanical packaging constraints and reducing the ESA cost, it is sometimes desirable to reduce the number of the T/R modules with a distribution beyond the half wavelength restriction.